1. Field of the Invention
The present invention relates to an ink ribbon cartridge which is optimally adapted for use in printing apparatus, and particularly to a cartridge which is continuously capable of preventing the ink ribbon wound on a pair of reels accommodated in the cartridge from slackening.
2. Description of the Prior Art
Recently, there have been proposed and developed various color printing apparatus which include a ribbon of colored ink consisting of a series of three coloured segments, such as a yellow, a fuchsin (magenta) acting as a red, and a cyanogen acting as a blue. As is well known, this ink ribbon is wound on a pair of reels, one being a supply reel and the other a take-up reel.
One such conventional ribbon cartridge for color printing apparatus will be described with reference to FIGS. 1 to 3. An ink ribbon cartridge 1 includes a cartridge body 2 formed of synthetic resin and a cartridge cover 3 also of synthetic resin. In general, the cartridge body 2 and the cartridge cover 3 are joined by ultrasonic welding. A pair of essentially cylindrical supply and take-up reels 8 and 9 are accommodated in an internal space defined between the cartridge body 2 and the cartridge cover 3. The cartridge body 2 has front and rear walls 2a and 2b opposing each other. The front wall 2a is formed with a pair of support sections 4 at both ends thereof for supporting one end of each of the reels 8 and 9. Each support section 4 has a semi-circular cut-out for receiving the outer peripheral surface of one end of a reel. Similarly, the rear wall 2b is formed with a pair of support sections 5 at both ends thereof for supporting the other ends of each of the reels 8 and 9. Each support section 5 has a projection for receiving the outer peripheral surface of the other end of a reel. The cartridge body 2 includes a pair of substantially semi-cylindrical storage sections 2c and 2d between the two pairs of support sections 4 and 5 for rotatably containing the two reels 8 and 9. The cartridge body 2 also includes an essentially rectangular opening 2e between the two storage sections 2c and 2d.
The cartridge cover 3 has front and rear walls 3a and 3b opposing each other. The front wall 3a is provided with a pair of support sections 6 at both ends thereof for supporting one end of each of the reels 8 and 9. Each support section 6 has a semi-circular cut-out which is associated with the semi-circular cut-out of the support section 4 to form a circular support portion serving to rotatably support one end of the reel. On the other hand, the rear wall 3b is provided with a pair of support sections 7 at both ends of thereof for supporting the other ends of the reels 8 and 9. Each support section 7 has a semi-circular cut-out which is associated with the projection of the support section 5 for journalling the other end of the reel. The cartridge cover 3 includes essentially semi-cylindrical storage sections 3c and 3d between the support sections 6 and 7 for rotatably receiving the two reels 8 and 9. The storage section 3c is associated with the storage section 2c to rotatably receive the supply reel 8, while the storage section 3d is associated with the storage section 2d to rotatably receive the take-up reel 9. The reels 8 and 9 receive a colored ink ribbon 10 comprising a repeating series of differently colored sections, for instance a yellow, a magenta, and a cyanogen section. The cartridge cover 3 also includes an essentially rectangular opening 3e between the two storage sections 3c and 3d.
As seen in FIG. 2. The reels 8 and 9 include flanges 8a and 9a fixed on and radially extending from one end of each reel respectively, and also include semi-spherical projections 8b and 9b axially extending from the other end of each reel respectively. The respective projections 8b and 9b are rotatably supported by the support sections 5 and 7. The two flanges 8a and 9a have a plurality of radially extending female sections 8c and 9c respectively, at the sides abutting the inner walls of the support sections 4 serving one end of the reels 8 and 9. As clearly seen in FIG. 3, the respective female sections 8c and 9c are radially and symmetrically arranged about the axes of the flanges 8a and 9a. The support sections 4 and 6 respectively include diametrically opposing ribs 4c and 6c which are capable of engaging with either one pair of diametrically opposing female sections 8c and 9c. A pair of coil springs 15 are disposed between the inner walls of the two pairs of support sections 5, 7 and the other ends of the reels 8, 9 in such a manner as to bias the two reels 8 and 9 in the right direction (as shown in FIG. 2), thereby causing the ribs 4c and 6c to normally engage the female sections 8c and 9c. In this manner, unnecessary rotation of the reels 8 and 9 is prevented by the engagement between the ribs 4c and 6c and the female sections 8c and 9c.
However, in such conventional ink ribbon cartridges for printing apparatus, when the cartridge is assembled, the engaging points between the female sections 8c, 9c of the two flanges 8a, 9a and the ribs 4c and 6c must be adjusted so as to tighten the ink ribbon 10, because even a small error such as a one pitch dislocation between the female sections 8c, 9c and the ribs 4c, 6c may cause excessive slack in the ink ribbon 10 due to the predetermined pitch between adjacent female sections. Furthermore, in such conventional ribbon cartridges, the engagement between the female sections 8c and 9c and the ribs 4c and 6c must be released during printing. For this reason, since the ribbon cartridge must be precisely inserted and positioned in a predetermined position and the above mentioned engagement must be released after insertion of the cartridge, more complicated constructions, such as a releasing mechanism for the above described engagement, are required in the printing apparatus. In addition, coil springs 15 are used in the cartridge assembly; these must be manually installed and mounted in the cartridge body 2 and the cartridge cover 3 during assembly of the body 2 and the cover 3, thereby deteriorating assembly efficiency for the ribbon cartridge. Additionally, parts such as coil springs are expensive.